But the British Medical Association (BMA) said that "systematic failures" by the company could be inhibiting GPs' abilities to provide safe care.

It said that GPs had told the union there are serious problems with the management of patient records including long delays with the collection and delivery of records, wrong records being delivered to practices, and problems processing urgent requests for records in a timely manner.

The BMA said that doctors had also reported problems with the supply of essential equipment such as prescription pads, fit note certificates and syringes to GP practices.

Dr Chaand Nagpaul, chair of the BMA's GP committee, said: "Clear evidence is emerging that there are a range of systematic and endemic failures in the way Capita are running crucial back office support services in general practice.

"Local GPs are reporting to the BMA that they are facing unacceptable delays in patient record transfers and mistakes in maintaining supplies of crucial medical equipment, like syringes and even prescription paper.

"These mistakes are directly impacting on the ability of many GPs to provide safe, effective care to their patients. They are in some cases being left without the essential information they need to know about a new patient and the tools to treat them.

"NHS England is ultimately responsible for the chaos caused by trying to cut the cost of this essential service for practices by privatising it and we can now all too clearly see the result, with practices picking up the workload and patients suffering as a result.

"I have written to NHS England expressing my grave concern about this state of affairs and received an apology for these failures. But we need urgent action to correct these shortcomings before patient care is further compromised."

A Capita spokeswoman said: "Across all PCSE services our focus is to ensure that GPs and primary care providers are supported so they can concentrate on patient care. We fully recognise that the services we provide play a key role in supporting primary care providers and apologise for the level and varied quality of service we have provided across a number of PCSE services.

"We are continuing to work closely with NHS England and our focus remains on delivering these important services at an optimum level.

"The pace, scale and complexity of introducing the changes NHS England requires to transform the PCSE service from a highly localised and inconsistent system, that was neither measured or monitored, to a more standardised and centralised model, is undoubtedly challenging and has resulted in some service users having varied and, on occasion, substandard experiences, for which we have openly apologised.

"We always prioritise urgent requests for medical records and if a paper-based medical record is unavailable, access to vital medical information is still available to GPs electronically without delay, or we assist direct GP-to-GP contact to ensure patient care is not disrupted as has always been the case."

An NHS England spokeswoman said: "We want to ensure GPs can focus on patient care and we acknowledge that Capita's provision of a number of support services for GP practices does not reflect the standard we expect.

"So we are working more closely with Capita to ensure that urgent and immediate improvements are made and this includes embedding a team of NHS England experts alongside Capita to more quickly identify and rapidly resolve issues.

"Capita has assured us they recognise the scale of the shortfalls, and are committed to resolving them as quickly as possible."